The invention relates to seals between moving members in fluid pressure systems wherein the fluid pressure varies on opposite sides of the seal. An effective seal often depends not only upon the configuration of the sealing members, but upon their frictional relationship to the other system components. It is known, for instance, to compose a seal of a relatively rigid member having low friction characteristics with a backup or loading static seal member of greater elasticity but with undesirable friction characteristics. However, there has been a problem with such composite seals in failure of the seal during certain conditions of fluid pressure change. The failures have been intermittent and unpredictable and it is not fully understood why they occur, but it is believed that a minute retraction of the dynamic seal from the sealing surface takes place when a fluid pressure change, either to a low pressure condition or to a balanced pressure condition, occurs even momentarily. The retraction from the sealing surface, even though incomplete, is believed to establish a fluid path between the sealed surface and the sealing ring with consequent undesirable affects.